Gas and water could be seen shooting into the air as crews responded to the scene and attempted to cap the main on Thursday morning.
The break happened around 9:30 a.m. on Summit Avenue near 25th and 26th streets.
PSE&G officials said initial reports, pending a full investigation, have found a contractor that was not hired by them was excavating when the damage occurred.
A spokesperson from Veolia said the water company was working on a repair of a water main at the time.
"While we were digging a gas main was hit that was mis-marked by PSE&G," the spokesperson said. "Our crew immediately notified Union City police which were already on the scene."
Veolia said because the water was overwhelming PSE&G crews, they got in and fixed the water main and PSE&G is still working to repair the gas line.
About 700 people were evacuated -- including residents as well as students and workers inside Union City High School.
Evacuation orders put in place after the rupture have since been lifted and residents were able to return home. A spokesperson with PSE&G said evacuations are a standard operating procedure with gas leaks.
The break created a gaping hole in the street and stirred fears among neighbors, who said they are thankful to law enforcement.
PSE&G said they cannot comment on if the gas line was mismarked until the investigation is complete.
Many streets have since reopened but residents can expect traffic delays in the immediate area as repairs continue.
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